The effects of the atmosphere on a propagating beam are modelled using the phase screen model, based in Kolmogorov's theory [1]}. The phase screen model is constructed by subdividing the atmosphere into regions of length \(\Delta h_i\) . For each region the random phase changes induced to the beam by the atmosphere are compressed into a phase screen. The phase screen is then placed at the start of the propagation length, and the rest of the atmosphere is taken to have a constant refractive index. The result at the end of the entire propagation length is a beam that has been deformed mimicking the effects of the turbulent currents in the atmosphere. Thus, this process recreates what a receiver with an intensity detector would observe. Numerically, the beam is represented by a uniform grid of pixels, each one assigned with a complex number, and the propagation is modelled via a Fourier algorithm [2]}.
Since the result of each beam propagation is random, the simulations are run 10,000 times, in order to obtain a correct estimation of the properties of the channel. A detailed description of the numerical methods used can be found elsewhere, e.g. [3]}, [4]}, [5]}.
